1. Field of Invention
This invention relates generally to computer graphics, and more particularly to a self-learning mechanism to establish a path through a set of nested graphics to facilitate the selection of a graphic display.
2. Status of Prior Art
Involved in computer graphics is communication between an operator and a computer wherein the input and output of the computer takes the form of charts, drawings or pictorial representations. Thus, a computer graphics display may be a line drawing of a two or three dimensional abstraction, the structural component of a building or a flow chart.
In an industrial process control system, the several process variables to be controlled, such as flow rate, pressure and temperature are sensed by individual transducers each included in a local process loop. In direct digital control, the several local control loops of a given installation are governed by a computer having a CRT display terminal on which one may graphically display the process being controlled and alphanumeric data relating thereto.
Thus, in a chemical processing plant in which, say, a process is carried out in a reactor into which is fed through respective control valves various chemicals and catalysts as well as steam under pressure derived from a steam generator, among the process variables are the flow rates of the inflowing chemicals into the reactor, the timing of the reaction, the level of temperature within the reactor, the flow rate of the product discharged from the reactor as well as the steam pressure. In a computer-controlled system, a schematic diagram or flow chart of the reactor process is graphically presented on the cathode ray tube tube (CRT) terminal before which is an operator console, making it possible for the operator to single out any process variable on the display and to exercise control thereover.
In order for an operator to select any process variable in a computer graphics display, the use of a cursor is conventional. A cursor is a symbol or special character serving as a pointer to allow interaction between the console operator and the program. It may take the form of a blinking luminous dot, an inverted V or caret, or any other distinctive symbol.
On a vector graphics console, the cursor symbol is usually manipulated by a manual input device such as a joystick, a data tablet, a trackball, a forcestick or a mouse. In the case of a joystick, for example, the operator can, as it were, drive the cursor around the screen to a point where it coincides with the exact X-Y location of the desired control point on the graphics display. It is also possible to manipulate cursor coordinates with a key matrix.
The concern of the present invention is with a set of nested graphics of the type appropriate to relatively elaborate industrial chemical plants, or any other installation in which the operating system is controlled from a central computer. When the system is highly complex and is composed of many interrelated sections or stages each having a multitude of process variables, it is not possible to encompass the entire system on a single graphics display in sufficient detail to include all action or control points in the system capable of being selected by a cursor.
To provide an adequate set of nested graphics for this purpose, the set may be in hierarchical form and include a primary graphic containing a general diagram of the entire system, secondary graphics each showing a respective section of the system in greater detail, and tertiary graphics each showing a respective sub-section of a given section. For a highly complex, system, it may be necessary to further sub-divide the tertiary graphics to provide additional graphics affording even more detailed showings. Or the set may be in non-hierarchical form and made up of various graphics each showing a section or sub-section of the system being controlled. The invention is not limited to any one form of nested graphics and encompasses any set whose graphics provide information in regard to a system or parts thereof that is computer controlled.
One commonly used method of CRT display selection at a computer terminal requires the operator to enter a character string at the keyboard to identify the desired display, this being followed by an ENTER or SELECT function. Another known method by which one can effect display selection is by positioning a cursor on the CRT screen. Also in use are paging techniques allowing movement through a pre-configured display.
When a problem arises in the computer-controlled installation and the operator finds it necessary to move back and forward through a nested set of graphics in search of a graphic in which the problem is located, all conventional methods capable of such movement are relatively slow. The reason for this is that the operator must repeat selections or be forced to view intermediate or undesired displays in the course of searching for the desired display.